[new proc macros]: doesn't support generic types in API definition.

[niklasad1]

For example this doesn't work:

#[rpc(client, server, namespace = "foo")]
pub trait Rpc<T> {
    #[method(name = "foo")]
    async fn async_method(&self, t: T);
}

pub struct RpcServerImpl;

#[async_trait]
impl<T> RpcServer<T> for RpcServerImpl {
    async fn async_method(&self, t: T) {
        todo!();
    }
}

[niklasad1]

Fixed by #436